This new proposal, Biodefense Training in Host-Pathogen Interactions, is intended as a seed project for rigorous scientific education of graduate students in the study of pathogenic microbes, their mechanisms of establishing human or animal infections, as well as the discovery of novel therapies or countermeasures that prevent human disease. The proposal draws on scientific strengths of University of Chicago faculty in the Committees on Microbiology and Immunology as well as on infrastructure provided through the recently established Great Lakes Regional Center of Excellence in Biodefense &Emerging Infectious Diseases, with resources in core structures that permit the study of pathogens via state of the art microscopy, mass spectrometry, immunology, animal infection and genomics facilities. Infrastructural commitments at the University of Chicago permit work on host-pathogen interactions in BSL-2 and BSL-3 laboratories, specifically designed for CDC select agents of categories A-C as well as on the Ricketts Regional Biocontainment Laboratory at Argonne National Laboratory, a federal laboratory that is constructed and operated by the University of Chicago for the National Institute of Allergy and Infectious Diseases. The commitment of University of Chicago faculty towards research and training excellence in biodefense and host-pathogen research is reflected in the recent establishment of the Department of Microbiology. Expansive growth with the appointment of seven new faculty over the next five years is accompanied by the recent expansion of graduate training in Microbiology and by the already excellent achievements of faculty and graduate students in this area. Sixteen training faculty study bacterial pathogenesis, animal viruses, viral physiology and pathogenesis, plant pathogenesis, drug resistant microbes, microbial toxins and the immune response to infections. Trainees are selected from a pool of 150 applicants with Bachelor's degree and average GRE and GPA scores of 1375+5 (81%) and 3.3 respectively. The ultimate goals of our training program are ambitious and aim at establishing a premier research program in biodefense and host-pathogen interactions.